Darlington went on to make over 80 professional appearances for the R's before then First Division side Wimbledon bought him for £200,000 in 2001. He made over 100 appearances for The Dons, before being released at the end of the 2003–04 season.

Brief stints at Watford and Cardiff City followed in 2004–05,[3][4] and 2005–06 however with a knee injury restricting his first-team chances Darlington left Cardiff in the summer of 2006, effectively retiring from professional football.

Following a trial with AFC Wimbledon, Darlington agreed terms with the Dons in time for the game against Tonbridge Angels on 18 November 2006,[5] making him the first ex-Wimbledon player to play competitively for AFC Wimbledon.[6]

This move would prove costly for the Dons however as, due to an administrative error by the club in signing him, Darlington was initially ineligible to play for the club.[7] The penalties the club received for this mistake were severe. The Dons were expelled from two cup competitions, the Surrey Senior Cup and the FA Trophy, for which the club was ordered to repay £12,000 in prize money, and also received a hefty penalty in the Isthmian League with 18 league points being docked,[8] in addition to a £400 fine & costs. This 18-point penalty was later reduced to just three points, after an appeal to The FA.[9] Darlington was released at the end of the 2006–07 season by new Dons boss Terry Brown.[10]

Darlington subsequently joined Isthmian League Division One South side Whitstable Town in March 2011, providing much needed cover and experience. Manager Peter Nott was quoted on the capture of Darlington: "As you can see Jermaine brings a wealth of experience with him and I am confident he will settle in very quickly."[12]

^NB: While Darlington was the first ex-Wimbledon FC player to play competitively for AFC Wimbledon he was actually the second ex-Wimbledon player to join the club. The first was Roger Joseph who was at the club briefly at the start of the 2005–06 season but left after playing a just handful of pre-season friendly fixtures.

^NB: When Darlington signed for AFC Wimbledon his previous club was Cardiff City. Cardiff play in the English League structure, which is administered by The FA of England. However, as with other Welsh clubs competing in the English leagues, the players of Cardiff City are actually registerred to the FA of Wales. As a result of this, when Darlington signed for AFC Wimbledon, his registration was not held by the FA but by the FAW and as such he was regarded as an 'international' signing and the club was therefore required to seek 'international clearance' for his registration to be transferred from one FA to the other. AFC Wimbledon were not aware of this and as a result Darlington was considered to be ineligible for competitive fixtures.